This Application claims foreign priority benefits under 35 U.S.C. xc2xa7 119(a)-(d) to German patent application 198 53 113.3, filed Nov. 18, 1998 by inventor, Bernhard Walter, for an invention entitled, xe2x80x9cGetriebexe2x80x9d(Transmission).
1. Field of Invention
This invention relates to improvements in power trains of the type wherein the means for transmitting torque from the rotary output element of a primary power source (such as an internal combustion engine) to a rotary driven element (such as the output shaft of an infinitely variable speed transmission) comprises a torque monitoring sensor integrated with such transmission, in which an endless flexible element (such as a belt or chain) is trained over a pair of adjustable pulleys or sheaves. Each pair of sheaves is adjustable by the torque sensor in response to abrupt changes in the transmitted torque to vary the transmission ratio. More particularly, the present invention relates to improvements in the axial positioning and mechanical attachment of the torque sensor, the adjustable sheaves and their corresponding hydraulic piston and cylinder assemblies on the drive shaft and output shaft of such a transmission. Still more particularly, the present invention discloses a one-sided attachment feature including retaining elements for attaching such hydraulic piston and cylinder assemblies and adjustable sheaves to the driven and output shafts of the infinitely variable speed transmission to locate the components in a fixed axial position when pressure is applied in a first direction and to permit axial movement of the components in an opposite direction to provide efficient operation thereof, to simplify assembly/disassenbly procedures, and to reduce manufacturing costs.
2. Description of the Related Art
Infinitely variable transmissions and torque monitoring devices or sensors of the above outlined character are disclosed, for example, in U.S. Pat. Nos. 5,725,447 and 5,879,253. The torque sensors, which are disclosed in these prior patents, are designed to establish a clamping engagement between component parts of a torque transmitting apparatus depending upon the load or depending upon the transmitted torque. As a rule such torque sensors are designed to ensure a frictional engagement between component parts, which are urged against or toward each other by a force depending upon the transmitted loads or upon the transmitted torque, in such a way that the force acting to urge the component parts into frictional engagement with one another at least approximates the force which is necessary for the transmission of torque. The application of an excessive force for urging the component parts against each other results in excessive wear whereas the application of an insufficient force entails a slip and hence again excessive wear between the parts which are maintained in frictional engagement with one another.
A conventional torque monitoring device or sensor includes a valve whose operation depends upon the magnitude of transmitted torque. Those portions of the torque sensor which are located downstream of a plenum chamber are constructed and assembled to comprise the aforementioned valve and the plenum chamber receives pressurized hydraulic fluid from a suitable pump. The valve acts as a flow restrictor or throttle, which seals the path for the flow of fluid from the plenum chamber so that the pressure of fluid in the plenum chamber increases in response to abrupt increases or peaks of transmitted torque. This results in a corresponding rise of fluid pressure in the plenum chamber as well as in the cylinder chamber or chambers of one or more piston and cylinder units. The piston and cylinder units are provided to adjust the infinitely variable transmission including a pair of adjustable tapered discs or sheaves and an endless flexible element, which is trained over and serves to transmit torque between the adjustable sheaves. The flexible element may constitute either a belt or a chain.
An increase in pressure in the cylinder chamber or chambers brings about a corresponding increase of the clamping force between the endless flexible element and the sheave or sheaves of the transmission. In other words, the frictional engagement between the sheave or sheaves on the one hand and the flexible element on the other hand increases in response to an increase of the transmitted torque and/or in response to the development of an abrupt increase of transmitted torque.
In order to adjust the above-described valve, the torque sensor comprises discs that are provided with confronting cam faces or ramps bearing upon rolling elements, which are retained between them with a force generated by the source of pressurized hydraulic fluid. If the transmitted torque develops abrupt increases or peaks, especially peaks in the torque being transmitted from the primary power source, the discs are caused to move axially and away from each other such that an axially movable portion reduces the effective cross-sectional area of the outlet for the flow of hydraulic fluid from the plenum chamber at a rate proportional to the magnitude of the peaks of transmitted torque.
In addition, the discs serve as a means for mechanically transmitting at least a portion of the driving torque to adjust the effective cross-sectional area of the outlet from the plenum chamber as a function of the magnitude of transmitted torque. Thus, the proper frictional clamping force between the adjustable sheaves and the endless flexible element of the infinitely variable transmission is maintained.
An infinitely variable ratio transmission, which can be utilized in conjunction with the improvements of the present invention as described hereinabove is disclosed in U.S. Pat. No. 5,169,365 to Friedmann and is incorporated herein by reference.
The disclosure in U.S. Pat. No. 5,879,253 entitled: xe2x80x9cTorque Monitoring Apparatusxe2x80x9d, filed Nov. 26, 1997 by inventors, Oswald Friedmann and Armin Veil, is hereby incorporated herein by this reference; and the disclosure in U.S. Pat. No. 5,725,447 entitled: xe2x80x9cPower Train with Infinitely Variable Ratio Transmissionxe2x80x9d, filed Dec. 14, 1995, by inventors, Oswald Friedmann, Urban Panther, and Ivo Agner, is also hereby incorporated herein by this reference.
Accordingly, the present invention is an improved infinitely variable speed transmission wherein the means for transmitting torque from the rotary output of a primary power source (such as an internal combustion engine) to a rotary driven element (such as the output shaft of an infinitely variable transmission) comprises a torque sensor integrated with such transmission, in which an endless flexible element (such as a belt or chain) is trained over a pair of adjustable pulleys or sheaves. The adjustable sheaves are adapted for axial movement on the driven and output shafts of the transmission being actuated by hydraulic piston and cylinder assemblies. The torque sensor is designed to axially shift the adjustable sheaves, which are urged towards each other by a force dependent upon the transmitted torque, into frictional engagement with the flexible element, which drives the output shaft of the transmission and transfers that force to the wheels of the vehicle.
The present infinitely variable speed transmission has been developed to simplify the installation of the torque sensor, the adjustable sheaves, and their respective piston and cylinder assemblies as well as to operationally improve such transmissions. This is accomplished by means of a novel, one-sided attachment feature, which is installed on both the driven and output shafts of the present transmission and which engages a mating structure formed on the shaft-mounted piston and cylinder assemblies to support the same in a fixed, non-rotatable position on the shaft.
In a preferred embodiment this novel attachment feature comprises a circular retaining element(s), which is radially disposed in a circumferential groove formed in both the driven and output shafts at a predetermined axial position. A mating projection formed on the shaft-mounted piston and cylinder assemblies engages the retaining element(s) during an assembly procedure of the transmission to secure the components in their functional position.
Advantageously, the retaining element(s) locate the components in a fixed axial position when pressure is applied in a first axial direction during operation of the transmission and permit axial movement in an opposite direction providing more efficient operation and simplifying assembly/disassembly procedures thereby reducing manufacturing costs.
In view of the above it is an object of the present invention to provide an improved infinitely variable speed transmission comprising an integrated torque sensor and having two adjustable sheaves and an endless flexible torque transmitting element trained over the sheaves, which can be utilized with advantage in the power trains of motor vehicles.
Another object of the present invention is to provide a novel, one-sided attachment feature for securing the torque sensor, the adjustable sheaves, and the shaft-mounted piston and cylinder units in a fixed axial position on the driven and output shafts of the transmission when pressure is applied in a first axial direction and to permit axial movement in an opposite direction.
Another object of the present invention is to provide a one-sided attachment feature as stated above wherein such attachment feature comprises a circular retaining element(s), which is radially disposed in a circumferential groove formed in such shafts and which engages a mating structure formed in the shaft-mounted piston and cylinder assemblies to secure the components in their functional position during operation.
Another object of the present invention is to provide a novel, one-sided attachment feature as stated above which simplifies the installation and assembly/disassembly procedures of the transmission and thereby reduces the manufacturing costs thereof.
Other features and technical advantages of the present invention will become apparent from a study of the following description and the accompanying drawings.